1. Field of the Invention
The present invention relates to an imaging apparatus and an imaging method which perform white balance control, and to a computer-readable recording medium in which a program for causing a computer to perform the imaging method is recorded.
2. Description of the Related Art
In the field of an imaging apparatus such as a digital steel camera or the like, white balance correction is performed to achieve constant color reproducibility even when color temperatures of a subject differ.
However, even with a technique related to this white balance correction, there is a problem that when an indoor scene is imaged, for example, an unnatural image as a whole is produced in which a blue sky seen from a window is white out although an image of a subject inside a room is good. This is because a dynamic range of the image is narrow.
Thus, in order to solve the problem, conventionally, the dynamic range of an image has been expanded by imaging and synthesizing two images. For example, a first short exposure image is captured by releasing the high-speed shutter, and, in succession, a second long exposure image is captured by releasing the low-speed shutter. Then, the two images are synthesized in such a manner that a scene outside the window which looks well in a low-sensitive image overlaps a high-sensitive image in which the scene in the room looks well.
Furthermore, Japanese Patent Application Publication No. 2004-48563 discloses a method using a white balance gain calculated from a high-power image as a white balance gain to be applied to both a high-power image and a low-power image before being synthesized, applied to a high-power image only, or applied to an image produced by synthesizing a high-power image and a low-power image, in an imaging apparatus which outputs an image of wide dynamic range by synthesizing a high-power image and a low-power image photographed by a solid-state imaging apparatus.
Still furthermore, Japanese Patent Application Publication No. 2004-120229 discloses a method applying a white balance gain calculated from a long exposure image for a white balance gain for an image in which a short exposure image and the long exposure image with their color balance adjusted are synthesized.
However, in the methods described above, a white balance gain set for a long exposure image is calculated only from a long exposure image. For this reason, white in a high-luminance part where a light source color is reflected better cannot be extracted from an image exposed for a time equal to or longer than an exposure time of an image captured by an imaging apparatus that does not use normal synthesis processing. Consequently, these methods have a problem that highly accurate white balance correction cannot be performed.